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Detection of and Defense against(Intercontinental Ballistic Missiles)
The first branching in the Lincoln Laboratory radar tree occurred in the mid-1950s in response to the rapid advances in ICBMs that the Soviet Union achieved 10. Lincoln Laboratory played a key role in shaping the architecture and choosing the radar approaches used in the Ballistic Missile Early Warning System, or BMEWS, which was installed at three sites: Thule, Greenland; Clear, Alaska; and Fylingdales Moor, United Kingdom. Lincoln Laboratory’s phase-coded pulse-modulation receiver/exciter for the VHF AN/FPS-17 radar, built at a site in eastern Turkey by the General Electric Company, allowed U.S. observers to monitor missile test launches from Kapustin Yar, deep within the Soviet Union. Subsequent installation of one or more AN/FPS-17 radars on Shemya, a western island in the chain of Aleutian Islands off Alaska, made it possible for U.S. observers to monitor Soviet missile test flights to the Kamchatka peninsula. The AN/FPS-17 radar was the first demonstration of pulse compression in an operational radar system 11. The 440-MHz UHF Millstone Hill radar, built by Lincoln Laboratory at Westford, Massachusetts, came into service in time to observe Sputnik I, the world’s first artificial satellite, which was launched by the Soviet Union on 4 October 1957. The race between the United States and the Soviet Union to demonstrate achievements in space was on. The Laboratory’s programs in space surveillance, satellite tracking, and space-object identification started at this time, and they continue to this day. The UHF Millstone Hill radar, which is shown in its original form in Figure 5 (and on the cover of this issue of the Journal), served as the model for several high-power, long-range radars built for the detection and tracking of ballistic missiles and for the collection of related data. One of these radars, installed at Prince Albert, Saskatchewan, Canada, was used to study auroral echoes, which are often encountered when a radar looks for ICBMs passing over arctic regions. Another such radar was installed on the island of Trinidad in the Caribbean, where it could observe missiles launched from Cape Canaveral, Florida. This radar served as the prototype for the missile trackers of BMEWS. By the early 1960s, the United States had embarked on its ballistic-missile-defense course, which continues to this day. The threat posed by Soviet ICBMs in this early era led to major radar developments by many other organizations, including the Bell Telephone Laboratories, Western Electric, the General Electric Company, and the Radio Corporation of America. Lincoln Laboratory’s research and development role in ballistic missile defense was concentrated on the problem of target discrimination during the reentry phase. The formidable task facing the defense was to identify the real warheads amidst the clutter of accompanying objects that can be part of an attack by ICBMs, and to perform this identification despite any countermeasures employed by the offense. The Laboratory’s approach to ballistic missile defense evolved in three directions. First, a reentrysimulation range was built on Katahdin Hill, adjacent to the main Laboratory buildings in Lexington, Massachusetts. Small objects, a few centimeters in size, of different materials were fired at ICBM reentry velocities by light-gas guns. The phenomena associated with the passage of these objects through the controlled atmospheres inside the test chambers were measured by radar and optical instrumentation. Analysis of the collected data provided a start on a scientific understanding of the physics of reentry 12. Second, at Wallops Island, Virginia, test objects of a few tens of centimeters in size were fired back into the atmosphere after having been launched above it by Trailblazer sounding rockets. Radar and optical instrumentation on the ground at Wallops Island, such as the radars shown in Figure 6, observed the accompanying physical phenomena during reentry 13. The Laboratory also developed and initially operated the Advanced Research Projects Agency (ARPA) Measurements Radar at White Sands Missile Range, New Mexico. That instrument was used to observe the reentry at ICBM speeds of larger objects fired back into the atmosphere by Athena sounding rockets launched from Green River, Utah. Third, the Department of Defense decided to establish a national center for ballistic missile testing at the Kwajalein Atoll in the middle of the Pacific Ocean. The U.S. Army and Bell Telephone Laboratories had already installed on Kwajalein a prototype version of the Nike-Zeus weapon system for defense against ICBMs. Long-range ballistic missiles could be launched to Kwajalein from Vandenberg Air Force Base on the west coast of California, about 7000 km away. Short-range missiles could be launched to Kwajalein from submarines and from Wake Island, about 1100 km north of Kwajalein. Lincoln Laboratory became the Scientific Director of Project PRESS (Pacific Range Electromagnetic Signature Studies), which was part of ARPA’s Project Defender. Under the Laboratory’s leadership, additional radar and optical instrumentation was installed on the island of Roi-Namur, on the northern tip of Kwajalein Atoll. The Laboratory operated the instrumentation radar and optics complex on Roi-Namur, analyzed the reentry data gathered during many launches, and distributed the results widely to the ballistic-missile-defense community. Lincoln Laboratory also developed and operated airborne optical instrumentation to observe the terminal phase of ballistic missile tests. Data gathered by this collection of tracking and measuring sensors were combined to provide a comprehensive understanding of the behavior of a reentering ICBM payload complex, which might typically include multiple warheads, decoys, and booster hardware. Attaining that understanding was critical for the development of effective ballistic-missile-defense systems. It was also critical to U.S. Air Force and U.S. Navy developers of ballistic missiles, wherein the steps to assure successful penetration of Soviet ballistic-missile-defense systems could be evaluated in a full-scale environment. The UHF/L-band TRADEX radar shown in Figure 7 was the first radar constructed at Roi-Namur Island. It was built by RCA under the technical direction of Lincoln Laboratory. TRADEX was followed by the VHF/UHF ALTAIR radar, shown in Figure 8, which was built by Sylvania, also under the technical direction of Lincoln Laboratory. These two radars were followed shortly by the C-band ALCOR radar, shown in Figure 9, which was built by Lincoln Laboratory with support from industry. ALCOR provided the nation’s first long-range wideband radar capability, and in the early 1970s it demonstrated the first high-resolution range-Doppler imaging of satellites. ALTAIR now has a space-surveillance mission as well as its ballistic-missile-defense role. These radars, operating at conventional radar frequencies, were later joined by millimeter-wave and laser radars. Not all ICBM launches of interest to the United States were aimed at Kwajalein Atoll. Early in the U.S. ICBM test program, radars were installed on ships that were stationed downrange from Cape Canaveral, Florida, to observe physical phenomena during reentry in the vicinity of the impact area. Seaborne radars such as these prefigured the Cobra Judy S-band phased-array radar shown in Figure 10, which was built by the Raytheon Corporation and installed on the USNS Observation Island in 1981. This potent resource could be moved wherever it was needed, such as to Kwajalein Atoll or to international waters off the Kamchatka Peninsula to observe the terminal phase of Soviet missile test flights 14. Lincoln Laboratory provided support to the Cobra Judy system in its developmental phase, and later became one of the principal analyzers of the data from this capable intelligence-collection radar. In 1996, in response to the needs of the U.S. theater- missile-defense community, Lincoln Laboratory designed and built a prototype transportable instrumentation radar, called Cobra Gemini. This radar system features wideband S-band and X-band radars that are packaged in air-transportable containers. Operational capability was achieved in March 1999 when the radar was installed on a Navy T-AGOS-class ship, the USNS Invincible, shown in Figure 11. There were a large number of ancillary developments related to missile defense that cannot be covered in this short review. One development that deserves an acknowledgment is the work on very high-power microwave components and high-power tubes. The Laboratory maintained a high-power test facility in the 1960s that contributed substantially to high-power microwave component and klystron development.